Conventionally, analyzers analyze a specimen by optically measuring a reaction liquid obtained by reaction between a specimen and a reagent while keeping the reaction liquid at a temperature as high as a human's body temperature. To that end, the analyzers include a reaction container holder which rotates while keeping a plurality of reaction containers for housing a reaction liquid at a constant temperature (see Patent Literature 1, for example). As for such a reaction container holder, it is known to include a retaining member having a plurality of retaining sections for retaining reaction containers, and a circular rotating member for detachably fixing the retaining member from above and rotating, where the retaining member can be removed from the rotating member for the cleaning of the retaining member.